Polishing pad comprising transmissive region

ABSTRACT

The invention provides a polishing pad comprising an optically transmissive region, wherein the polishing pad comprises a polishing pad body comprising an opaque first region and an optically transmissive second region, wherein the second region has at least one recess formed therein of at least one part of the polishrag pad body, and at least one translucent window insert is integrated into the at least one recessed area. The polishing pad body and the at least one translucent window insert comprise different porous. materials.

BACKGROUND OF THE INVENTION

Chemical-mechanical polishing (“CMP”) processes are used in themanufacturing of microelectronic devices to form flat surfaces onsemiconductor wafers, field emission displays, and many othermicroelectronic substrates. For example, the manufacture ofsemiconductor devices generally involves the formation of variousprocess layers, selective removal or patterning of portions of thoselayers, and deposition of yet additional process layers above thesurface of a semiconducting substrate to form a semiconductor wafer. Theprocess layers can include, by way of example, insulation layers, gateoxide layers, conductive layers, and layers of metal or glass, etc. Itis generally desirable in certain steps of the wafer process that theuppermost surface of the process layers be planar, i.e., flat, for thedeposition of subsequent layers. CMP is used to planarize process layerswherein a deposited material, such as a conductive or insulatingmaterial, is polished to planarize the wafer for subsequent processsteps.

In polishing the surface of a substrate, it is often advantageous tomonitor the polishing process in situ. One method of monitoring thepolishing process in situ involves the use of a polishing pad having anaperture or window. The aperture or window provides a portal throughwhich light can pass to allow the inspection of the substrate surface byan optical detection system during the polishing process. Polishing padshaving apertures or windows are known and have been used to polishsubstrates, such as semiconductor devices. For example, U.S. Pat. No.6,171,181 discloses a polishing pad comprising a one-piece moldedarticle having a translucent region and an opaque region. Thetranslucent region is formed by solidification of a flowable polymericmaterial which is initially translucent so that a portion of thepolymeric material retains its transparency after solidification. Rapidcooling of a region of the flowable polymeric material results insolidification of the region to minimize crystallization of the materialin the region and to provide the amorphous translucent region. U.S. Pat.No. 6,840,843 discloses a polishing pad comprising a translucent region,wherein the translucent region is prepared by compressing a region of aporous polymeric polishing pad substrate so as to provide thetranslucent region.

However, the apertures or windows often have properties that differ fromthe rest of the polishing pad, such as porosity, hardness, resistance towear, and the like. These property differences often lead to non-uniformpolishing of substrates. Additionally, apertures or windows havetypically been designed to allow maximum transmission of light to thetarget substrate and to the detector. This fact does not take intoconsideration that different substrates and different detectors mayrequire a different quality or quantity of light for optimum end pointdetection. Thus, there remains in the art a need for improved polishingpads with optically transmissive regions.

BRIEF SUMMARY OF THE INVENTION

The invention provides a polishing pad comprising an opticallytransmissive region, wherein the polishing pad comprises (a) a polishingpad body comprising a first region and a second region, wherein thefirst region is opaque, wherein the second region is opticallytransmissive, wherein the second region has at least one recess formedtherein, and (b) at least one translucent insert integrated into the atleast one recess, wherein the polishing pad body comprises a firstporous material and the at least one translucent insert comprises asecond porous material that differs from the first porous material.

The invention also provides a method for making a polishing pad havingan optically transmissive region, comprising the steps of (a) providinga polishing pad body, wherein the polishing pad body comprises a firstporous material, (b) forming at least one recess within the polishingpad body of at least one part of the polishing pad body, (c) providingat least one translucent insert, wherein the translucent insertcomprises a second porous material that differs from the first porousmaterial, and (d) adhering the at least one translucent insert to therecess to provide a polishing pad having at least one opticallytransmissive region.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a cross-sectional view of a polishing pad in accordance withan embodiment of the invention.

FIG. 2 is a cross-sectional view of a polishing pad in accordance withan embodiment of the invention.

FIGS. 3A-3C depicts representative surface textures of translucentwindows in accordance with certain embodiments of the invention.

FIG. 4 is a cross-sectional view of a polishing pad in accordance withan embodiment of the invention.

FIG. 5 is a cross-sectional view of a polishing pad in accordance withan embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a polishing pad comprising an opticallytransmissive region. The polishing pad comprises (a) a polishing padbody comprising a first region and a second region, wherein the firstregion is opaque, wherein the second region is optically transmissive,wherein the second region has at least one recess formed therein, and(b) at least one translucent insert integrated into the at least onerecess, wherein the polishing pad body comprises a first porous materialand the at least one translucent insert comprises a second porousmaterial that differs from the first porous material.

The polishing pad can have any suitable dimensions. Typically, thepolishing pad is circular in shape (as is used in rotary polishingtools) or is produced as a looped linear belt (as is used in linearpolishing tools). Preferably, the polishing pad is circular.

The polishing pad body can comprise any suitable material. Desirably,the polishing pad body comprises a polymer resin. The polymer resin canbe any suitable polymer resin. Typically, the polymer resin is selectedfrom the group consisting of thermoplastic elastomers, thermosetpolymers, polyurethanes (e.g., thermoplastic polyurethanes), polyolefins(e.g. thermoplastic polyolefins), polycarbonates, water soluble polymerslike polyethyleneoxide, glycols, poly(vinyl alcohols), biodegradablepolymers such as poly(lactic acid), poly(hydroxyl butyrate), polymerswhich are crosslinkable by UV or gamma radiation, polysilicones,polysiloxanes, polyvinylalcohols, nylons, elastomeric rubbers,elastomeric polyethylenes, polytetrafluoroethylenes,polyethyleneterephtalates, polyimides, polyaramides, polyarylenes,polyacrylates, polystyrenes, polymethylmethacrylates, copolymersthereof, and mixtures thereof. Preferably, the polymer resin is apolyurethane, more preferably, a thermoplastic polyurethane.

The polishing pad body can be produced using any suitable technique,many of which are known in the art. For example, the polishing pad bodycan be formed by methods such as casting and extrusion. The polymerresin may be a thermoplastic material which is heated to a temperatureat which it will flow and is then formed into a desired shape by castingor extrusion. The polymer resin may provide a porous structure by itsnatural configuration. In other embodiments, the porous structure may beintroduced through the use of various production techniques known in theart (e.g., foaming, blowing, and the like). Representative methodsproviding a porous structure comprising closed-cell pores includefoaming processes such as a supercritical fluid (SCF) process, a phaseinversion process, a spinodal or bimodal decomposition process, or apressurized gas injection process, all of which are well known in theart. A representative method providing a porous structure comprisingopen-cell pores comprises sintering particles of a thermoplasticpolymer, such as a polyurethane, to provide an open-cell porousstructure.

The pad comprises a body comprising a first region and a second region,wherein the first region is opaque, and wherein the second region isoptically transmissive. The first region of the polishing pad body isporous and has a first void volume. The first void volume is non-zeroand can be any suitable non-zero void volume. For example, the firstvoid volume can be 5% or more (e.g., 10%% or more, or 20% or more, or30% or more, or 40% or more). Alternatively, or in addition, the firstvoid volume can be 70% or less (e.g., 60% or less, or 50% or less, or45% or less, or 40% or less). The first void volume can be bounded byany two of the aforementioned void volumes. Thus, for example, the firstvoid volume can be 20% to 70%, or 20% to 60%, or 20% to 50%, or 25% to70%, or 25% to 60%, or 25% to 50%.

The first region of the polishing pad body can have any suitable averagepore size. For example, the first region of the polishing pad body canhave an average pore size of 500 μm or less (e.g., 300 μm or less, or200 μm or less). In one preferred embodiment, the first region of thepolishing pad body has an average pore size of 50 μm or less (e.g., 40μm or less, or 30 μm or less). In another preferred embodiment, thefirst region of the polishing pad body has an average pore size of 1 μm,to 20 μm (e.g., 1 μm to 15 μm, or 1 μm to 10 μm).

Typically the first region of the polishing pad body comprisespredominantly closed cells (i.e., pores); however, the first region ofthe polishing pad body can also comprise open cells. Preferably, thefirst region of the polishing pad body comprises 5% or more (e.g., 10%or more) closed cells based on the total void volume. More preferably,the first region of the polishing pad body comprises 20% or more (e.g.,30% or more, 40% or more, or 50% or more) closed cells based on thetotal void volume.

The second region of the polishing pad body can be porous, substantiallynon-porous, or completely non-porous. The second region of the polishingpad body typically has a void volume which is smaller than the voidvolume of the first region of the polishing pad body.

The first region of the polishing pad body is substantially or entirelyopaque. In one embodiment, a portion of the polishing pad body, which issubstantially or entirely opaque, is compressed to form a second regionof the polishing pad body that is optically transmissive. The term“optically transmissive” as used herein, refers to the ability totransmit at least a portion of light contacting the surface of thepolishing pad and can be used to describe slightly, partially,substantially, and completely translucent or transparent materials. Theat least one second region of the polishing pad body preferably is atleast optically transmissive to light having a wavelength of 390-3500nm, more preferably visible light, and most preferably visible lightfrom a laser light source, particularly as used in a polishing device tobe used with the polishing pad.

Without wishing to be bound by any particular theory, it is believedthat the pores in the polishing pad body cause light passing through theporous structure to scatter, thereby reducing the translucency of thepolishing pad body or rendering the polishing pad body opaque. Thedegree of light scattering is believed to be a function of average poresize and average pore volume. It is further believed that compressingthe polishing pad body reduces the light-scattering effect of the poresby reducing the porosity of the polishing pad body in the region that iscompressed. As a result, the compressed region (i.e., the second regionof the polishing pad body) has an increased light transmittance (i.e.,decreased level of light scattering and increased translucence) ascompared to the polishing pad body that is not compressed (i.e., thefirst region of the polishing pad body).

As will be appreciated by those of ordinary skill in the art, the degreeof translucence provided in this manner will depend, at least in part,on the degree to which the porous polymer structure is compressed (i.e.,the degree to which the porosity of the porous polymer structure isreduced). For example, the polishing pad body can be compressed by10-50% (e.g., 20-40%) of its thickness prior to compression (i.e., thenon-compressed thickness of the polishing pad body).

Compression of the polishing pad body to form at least one recess can beperformed in any suitable manner known in the art. As will beappreciated by those of ordinary skill in the art, the most effectivetechnique of compression will depend, at least in part, on theparticular polymer used in the fabrication of the polishing pad body.The polishing pad body can be compressed, for example, by use of RFwelding techniques, by use of calendar rollers, or by use of variouspressing mechanisms known in the art, such as a platen press, stampingmachine, and the like. Furthermore, heat can be used, either alone or inconjunction with other compression techniques, to achieve a compressedstructure. For example, the polishing pad body can be heated to atemperature approaching, meeting, or exceeding its softening or meltingtemperature for a time sufficient to allow the pores of the secondregion of the polishing pad body to collapse under the weight of thepolymer used in the construction of the polishing pad body.Alternatively, heat can be applied to the polishing pad body before,during, or after compressing of the polishing pad body using anothercompression technique. For example, an RF welding process can use a dieor dies in conjunction with application of radiofrequency energy in themegahertz region to cause beating of the polishing pad body that is incontact with the die or dies to cause compression of the region of thepolishing pad body. In another example, a heated press or heated rollerscan be used to compress the polishing pad body so as to compress aregion of the polishing pad body. When using heat in conjunction withanother compression technique to compress the polishing pad body, thepolishing pad body is preferably heated to a temperature thatapproaches, meets, or exceeds the softening or melting temperature ofthe polishing pad body.

In another embodiment, the second region of the polishing pad body isprovided with at least one recess, wherein the at least one recess isformed in one face (i.e. one surface) of the polishing pad body. Thesaid recess, or recessed area, can be formed by removing pad materialfrom the face of the pad using any suitable manner, such as with the useof a router tool. In one embodiment the material is removed from therecess area via a rotary cutting tool which is mounted on a computernumerical controlled (CNC) router table. Depth of cut, position of therecess, rotational speed of the cutting tool and planarity of the recessare controlled by a programming code. In another embodiment, the secondregion of the polishing pad body is provided with a first recess and asecond recess, wherein the first and second recesses are formed byremoving pad material on opposite faces of the polishing pad body.

The polishing pad comprises at least one translucent insert integratedinto the at least one recessed area. The translucent window comprises aporous material that is different from the material used in thepreparation of the polishing pad body. The translucent insert cancomprise any suitable material. Desirably, the translucent insertcomprises a polymer resin. The polymer resin can be as described hereinfor use in the preparation of the polishing pad body. Preferably, thepolymer resin used in the preparation of the translucent insert is athermoplastic polymer.

FIG. 1 depicts an embodiment of the inventive polishing pad. The insert20 is integrated into a recess in the polishing pad body to form atransmissive region. A subpad 30 is affixed to the bottom surface ofpolishing pad body 10.

The translucent insert can be prepared using any suitable method, suchas any of the methods described herein for the preparation of thepolishing pad body. In a preferred embodiment, the translucent insert isprepared by casting or extrusion of a thermoplastic polymer resin (e.g.,a thermoplastic polyurethane), followed by pressurized gas injectionprocess. For example, the thermoplastic polymer resin can be extruded toprovide a sheet of window blank material, which is then subjected tohigh pressure carbon dioxide in a pressure chamber, followed by heatingto cause absorbed carbon dioxide to expand and to foam the polymerresin. This insert material is then die cut to the final shape of therecess on the face of the polishing pad body and integrated into therecess using RF welding.

The translucent insert has a void volume that is non-zero. For example,the void volume of the translucent insert can be 1% or more (e.g., 2% ormore, or 3% or more, or 4% or more, or 5% or more). Alternatively, or inaddition, the void volume of the translucent insert can be 25% or less(e.g., 20% or less, or 15% or less). The void volume of the translucentinsert can be bounded by any two of the aforementioned void volumes.Thus, for example, the void volume of the translucent insert can be 1%to 25%, or 1% to 20%, or 1% to 1.5%, or 1% to 10%, or 25% to 60% or 25%to 50%.

The translucent insert can have any suitable average pore size. Forexample, the translucent insert can comprise pores having an averagepore size of 50 μm or less (e.g., 40 μm or less, or 30 μm or less). In apreferred embodiment, the translucent insert comprises pores having anaverage pore size of 1 μm to 20 μm (e.g., 1 μm to 15 μm, or 1 μm to 10μm).

Typically the translucent insert comprises predominantly closed cells(i.e., pores); however, the translucent insert can also comprise opencells. Preferably, the translucent insert comprises 5% or more (e.g.,10% or more) closed cells based on the total void volume. Morepreferably, the translucent insert comprises 20% or more (e.g., 30% ormore, 40% or more, or 50% or more) closed cells based on the total voidvolume.

The translucent insert can be integrated into the at least one recess byuse of any suitable technique. Non-limiting examples of suitabletechniques include welding techniques and the use of adhesives.Preferably, the translucent insert is integrated into the at least onerecess by use of a welding technique, more preferably by use of RFwelding or ultrasonic welding. RF welding involves positioning atranslucent insert to be welded into a recess on the polishing pad bodyand using a die to direct the welding process. High frequency waves inthe megahertz scale are passed through the materials with the resultthat the pieces are heated and the translucent insert becomes integratedinto the recess. Ultrasonic welding involves the use of high frequencysound waves to melt the materials comprising the translucent window andthe polishing pad body in the recess and thereby cause the materials toflow together so that the translucent insert becomes integrated into therecess. Typically, the source of ultrasonic waves is a sound-generatingmetal tuning device (e.g., a “horn”) that converts a high-frequencyelectrical signal into sound in the kilohertz scale, although anysuitable source of ultrasonic sound can be used. The horn can be anysuitable horn, for example, a stainless steel horn. The horn can haveany suitable shape or configuration and preferably is machined to have asimilar shape, or even an identical shape, to the shape of thetranslucent insert.

In certain embodiments, the translucent insert is formed in situ in arecess in the polishing pad body. After formation of the recess, aprecursor to the translucent insert is placed within the recess and thenconverted into the translucent insert. For example, particles of athermoplastic polyurethane can be placed into the recess, followed byheating and/or compression, such as by use of RF welding, to provide asintered translucent insert integrated into the recess.

In certain embodiments, the polishing pad comprises at least twotranslucent inserts integrated into recesses formed in opposite faces ofthe polishing pad body, which translucent inserts desirably are alignedwith each other. In these embodiments, the at least two translucentinserts can be the same or different. The at least two translucentinserts can comprise the same or different polymer resins. When the atleast two translucent inserts are different, the translucent insertwhich is on the front face of the polishing pad is porous, while thetranslucent insert which is opposite to the front face of the polishingpad may be porous or may be substantially or even completely nonporous.

FIG. 2 depicts an embodiment of the inventive polishing pad comprisingtwo translucent inserts. Translucent inserts 20 and 40 are aligned andintegrated into opposing recesses on polishing pad body 10. A subpad 30is affixed to the bottom surface of polishing pad body 10.

In some embodiments, the translucent insert has a surface texture. Thesurface texture facilitates the lateral transport of a polishingcomposition, or the abrasive particles across the surface of thetranslucent window. The surface texture can be provided using anysuitable technique, an example of which is through embossing the surfaceof the translucent window. Embossing can provide a variety of patternsas depicted in FIGS. 3A-3C. For example, embossing can be used to createa dimple pattern as depicted in FIG. 3A, a hexagonal pattern as depictedin FIG. 3B, or a reversed hexagonal pattern as depicted in FIG. 3C.Other suitable surface texture patterns can be readily envisioned by oneof ordinary skill in the art.

The surface texture can be embossed into a surface of the translucentwindow by using an RF welding tool having features that transfer to thesurface of the translucent window during the welding process tointegrate the translucent window into the polishing pad body.Alternatively, the surface texture can be embossed into a surface of thetranslucent insert prior to integration into the polishing pad body. Inaddition, the formation of a surface texture on the surface of a foamedtranslucent insert typically results in the formation of higher andlower porosity regions within the translucent insert corresponding tothe different degrees of compression that result in formation of thetexture pattern.

The surface texture of the translucent insert can be tailored to providea desired amount of light transmission. The presence of a surfacetexture can result in greater light scattering of an incident beam ofradiation, thus the density and type of surface texture can be selectedto provide the desired light transmission properties. In addition,alteration of the degree of porosity of the translucent window by, forexample, embossing also can affect light scattering caused by pores.

The translucent insert optionally contains soluble particlesincorporated into the translucent insert. When present, the solubleparticles preferably are dispersed throughout the translucent insert.Such soluble particles partially or completely dissolve in the liquidcarrier of the polishing composition during chemical-mechanicalpolishing. Typically, the soluble particles are water-soluble particles.For example, the soluble particles can be any suitable water-solubleparticles, such as particles of materials selected from the groupconsisting of dextrins, cyclodextrins, mannitol, lactose,hydroxypropylcelluloses methylcelluloses, starches, proteins, amorphousnon-cross-linked polyvinyl alcohol, amorphous non-cross-linked polyvinylpyrrolidone, polyacrylic acid, polyethylene oxide, water-solublephotosensitive resins, sulfonated polyisoprene, and sulfonatedpolyisoprene copolymer. The soluble particles also can be inorganicwater-soluble particles, such as particles of materials selected fromthe group consisting of potassium acetate, potassium nitrate, potassiumcarbonate, potassium bicarbonate, potassium chloride, potassium bromide,potassium phosphate, magnesium nitrate, calcium carbonate, and sodiumbenzoate. When the soluble particles dissolve, the translucent windowcan be left with open pores corresponding to the size of the solubleparticles.

In an embodiment, the translucent insert comprises a first thermoplasticpolymer and a second thermoplastic polymer, wherein the first and secondthermoplastic polymers are immiscible and form distinct phases withinthe translucent insert. The refractive index of the translucent insertwill depend on the refractive indices of the thermoplastic polymers usedin its formation and their relative amounts and can be varied based onthe aforesaid parameters.

The translucent insert can be of any suitable shape, dimension, orconfiguration. For example, the translucent insert can have the shape ofa circle, an oval, a rectangle, or a square. When the translucent insertis oval or rectangular in shape, the insert typically has a maximumlength of 3 cm to 8 cm. When the translucent insert is circular orsquare in shape, the translucent insert typically has a diameter orwidth of 1 cm to 4 cm. The translucent insert typically has a thicknessof 0.1 cm to 5 cm (e.g., 0.1 cm to 3 cm, or 0.1 cm to 1 cm).

The polishing pad can comprise any suitable number of translucentinserts. The translucent insert or inserts can be positioned in anysuitable location of the polishing pad body.

In an embodiment, the polishing pad further comprises a wear indicatorlocated in the transmissive region. The wear indicator desirably changesthe end point signal generated by the polishing apparatus to providenotice that the polishing pad is ready to be changed for a new polishingpad. The window wear indicator typically is integrated into the recessedarea of the pad between the recessed area and the translucent insert.Non-limiting examples of suitable wear indicators include a coloredthermoplastic urethane layer, a polarized thermoplastic urethane layer,a thermoplastic urethane layer comprising a fluorescing agent, a polymerlayer with unique light transmission properties, an oxidized layer, apolymer comprising thermochromic dyes, a moisture indicating layer fordetection of window leaks, and a wavelength filtering layer. FIG. 4depicts an embodiment of the inventive polishing pad comprising opposingtranslucent inserts 20 and 40 integrated into polishing pad body 10,with wear indicator 50 interposed between translucent insert 20 andpolishing pad 10. A subpad 30 is affixed to the bottom surface ofpolishing pad 10.

When the polishing pad comprises two translucent inserts oppositelydisposed from one another and integrated into first and second recessesformed on opposite faces of the polishing pad body, the translucentinsert integrated into the back surface of the polishing pad can becoplanar with the back surface of the polishing pad, recessed from theback surface of the polishing pad, or can extend beyond the back surfaceof the polishing pad. A translucent insert that extends beyond the backsurface of the polishing pad is depicted in FIG. 5. A first translucentinsert 20 is integrated into a first recess on the polishing surface ofpolishing pad body 10 and is coplanar with the polishing surface, and asecond translucent insert 40 is integrated into a second, oppositerecess on the bottom surface of the polishing pad body 10 and extendsbeyond the bottom surface of polishing pad body 1.0. In use, compressionof the affixed subpad 30 by a platen (not shown) allows the platen toapply pressure to the second translucent insert 40. The pressure appliedto the second translucent insert 40 is transmitted to the firsttranslucent insert 20 and can help prevent an air pocket from formingbetween first translucent insert 20 and a substrate being polished.

A polishing pad in accordance with the invention can be used alone oroptionally can be used as one layer of a multi-layer stacked polishingpad, as illustrated in FIGS. 1, 2, 4, and 5. For example, the inventivepolishing pad can be used in combination with a subpad. The subpad canbe any suitable subpad. Suitable subpads include polyurethane foamsubpads, impregnated felt subpads, microporous polyurethane subpads, orsintered urethane subpads. The subpad typically is softer than thepolishing pad of the invention and therefore is more compressible thanthe polishing pad. In some embodiments, the subpad is harder and is lesscompressible than the polishing pad. The subpad contains at least onewindow or aperture to expose the transmissive region of the polishingpad. The subpad optionally comprises grooves, channels, hollow sections,and the like. When the polishing pad of the invention is used incombination with a subpad, typically there is an intermediate backinglayer such as a polyethyleneterephthalate film, coextensive with andbetween the polishing pad and the subpad.

A polishing pad of the invention has a polishing surface whichoptionally further comprises grooves, channels, and/or perforationswhich facilitate the lateral transport of a polishing composition acrossthe surface of the polishing pad. Such grooves, channels, orperforations can be in any suitable pattern and can have any suitabledepth and width. The polishing pad can have two or more different groovepatterns. For example, a combination of large grooves and small groovescan be used. The grooves can be in the form of slanted grooves,concentric grooves, spiral or circular grooves, XY crosshatch pattern,and can be continuous or non-continuous in connectivity. Preferably, thepolishing pad has a polishing surface that comprises at least smallgrooves produced by standard pad conditioning methods. Typically, thetranslucent window is not provided with the same grooves, channels,and/or perforations as for the polishing pad.

The invention further provides a method of polishing a substrate, whichmethod comprises (i) providing a substrate to be polished, (ii)contacting the substrate with a polishing system comprising theinventive polishing pad described herein and a polishing composition,and (iii) abrading at least a portion of the substrate with thepolishing system to polish the substrate.

The polishing composition can be any suitable polishing composition. Thepolishing composition typically comprises an aqueous carrier, a pHadjustor, and optionally an abrasive. Depending on the type of workpiecebeing polished, the polishing composition optionally can furthercomprise oxidizing agents, organic acids, complexing agent, pH buffers,surfactants, corrosion inhibitors, anti-foaming agents, and the like.

The following examples further illustrate the invention but, of course,should not be construed as in any way limiting its scope.

Example 1

This example demonstrates the effect of the texturing patterns of thetranslucent insert on the % transmission of laser light through atransmissive region of a polishing pad of the present invention.

Samples were prepare by cutting pieces of a porous polyurethane foampolishing pad (D-200, Cabot Microelectronics, Aurora, Ill.) and forminga recess on the polishing surface side using a router tool. The recesseswere 30 mil deep and formed in a oblong shape. The polishing pad pieceswere between 53 and 56 mil thick.

Translucent inserts of thermoplastic polyurethane having a Shore Dhardness of 55 were prepared with different texture patterns formed ontheir surfaces. The texture was formed by An RF welding process usingpatterned aluminum tools. The pattern was formed either by laserengraving or by chemical etching of the aluminum tool surface. The toolpatterns were made by Mold-Tech Inc. (Carol Stream, Ill.). Thetranslucent inserts were then integrated into the recesses formed in thepolishing pad pieces by RF welding to form the transmissive regions fortesting.

Laser light from a 655 nm laser light source was directed through eachof the transmissive regions being tested. The laser light transmittedwas detected using a Newport optical power meter, model 1931-C (NewportCorporation, Irvine, Calif.). The results of the tests are shown inTable 1. The pattern number of the Mold-Tech tool is given as referencewith the description of the texture pattern. As can be seen from thedata, a wide range of % transmission values can be generated dependingon the pattern chosen for the translucent insert. Different patternedinserts can thus be selected, and hence different transmissive regionsformed in polishing pads, to provide the optimum % transmission tooptimize end point detection for the polishing application.

TABLE 1 Pattern Description M-T number % Transmission No texture N.A.44.5 Small grid MT-11640 14.5 Dimple pattern MT-11605 8.9 Reverse HexMT-11610 3.0 Hex patterns MT-11600 2.5 Large grid MT-11475 1.4 Randompattern MT-11430 1.3 Random pattern MT-11570 2.8 Random pattern MT-110503.2

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. A polishing pad comprising an optically transmissive region, whereinthe polishing pad comprises: (a) a polishing pad body comprising a firstregion and a second region, wherein the first region is opaque, whereinthe second region is optically transmissive, wherein the second regionhas at least one recess formed therein, and (b) at least one translucentinsert integrated into the at least one recess, wherein the polishingpad body comprises a first porous material and the at least onetranslucent insert comprises a second porous material that differs fromthe first porous material.
 2. The polishing pad of claim 1, wherein thepolishing pad body comprises a first thermoplastic polymer and the atleast one translucent insert comprises a second thermoplastic polymerthat differs from the first thermoplastic polymer.
 3. The polishing padof claim 1, wherein the translucent insert comprises a firstthermoplastic polymer and a second thermoplastic polymer, and whereinthe first and second thermoplastic polymers are immiscible and formdistinct phases within the translucent window.
 4. The polishing pad ofclaim 1, wherein the translucent insert further comprises particles of amaterial that differs from the second porous material.
 5. The polishingpad of claim 4, wherein the particles comprise a material that issoluble in water.
 6. The polishing pad of claim 1, wherein thetranslucent insert has a void volume of 0.1% to 10%.
 7. The polishingpad of claim 1, wherein the translucent insert has a polishing surfacewith a texture.
 8. The polishing pad of claim 1, wherein the secondregion has a first recess and a second recess formed therein, andwherein the first recess has a first translucent insert integratedtherein, and the second recess has a second translucent insertintegrated therein.
 9. The polishing pad of claim 8, wherein the face ofthe polishing pad body comprising the second recess defines a plane, andwherein a surface of the second translucent insert is substantiallycoplanar with the plane.
 10. The polishing pad of claim 8, wherein theface of the polishing pad body comprising the second recess defines aplane, and wherein a surface of the second translucent insert extendsbeyond the plane.
 11. A method for making a polishing pad having anoptically transmissive region, comprising the steps of: (a) providing apolishing pad body, wherein the polishing pad body comprises a firstporous material, (b) forming at least one recess within the polishingpad body, (c) providing at least one translucent insert, wherein thetranslucent insert comprises a second porous material that differs fromthe first porous material, and (d) adhering the at least one translucentinsert to the recess to provide a polishing pad having at least oneoptically transmissive region.
 12. The method of claim 11, wherein thepolishing pad body comprises a first thermoplastic polymer and the atleast one translucent insert comprises a second thermoplastic polymerthat differs from the first thermoplastic polymer.
 13. The method ofclaim 11, wherein the translucent insert comprises a first thermoplasticpolymer and a second thermoplastic polymer, and wherein the first andsecond thermoplastic polymers are immiscible and form distinct phaseswithin the translucent insert.
 14. The method of claim 11, wherein thetranslucent insert further comprises particles of a material thatdiffers from the second porous material.
 15. The method of claim 11,wherein the translucent insert is formed prior to adhering thetranslucent insert to the recess.
 16. The method of claim 11, whereinthe translucent insert is formed by placement of a precursor of thetranslucent insert within the recess and then conversion of theprecursor to the translucent insert.
 17. The method of claim 11, whereinthe step of forming a recess within the polishing pad body comprises useof an energy input selected from the group consisting of pressure, heat,radio frequency irradiation, ultrasonic welding, and combinationsthereof.
 18. The method of claim 11, wherein the step of forming arecess within the polishing pad body comprises use of a router tool. 19.The method of claim 11, wherein the step of adhering the at least onetranslucent insert to the recess comprises use of an energy inputselected from the group consisting of solvent adhesion, pressure, heat,radio frequency irradiation, ultrasonic welding, and combinationsthereof.
 20. The method of claim 1, wherein the translucent insert has apolishing surface with a texture.